mollusc vs mollusk

mollusc and mollusk both are nouns.

Word	Noun	Adjective	Verb	Adverb
mollusc	Yes	No	No	No
mollusk	Yes	No	No	No

As nouns, mollusc and mollusk are synonyms defined as:

mollusc and mollusk: invertebrate having a soft unsegmented body usually enclosed in a shell

Other synonyms of mollusc include shellfish.

mollusc (noun)	mollusk (noun)
invertebrate having a soft unsegmented body usually enclosed in a shell	invertebrate having a soft unsegmented body usually enclosed in a shell